This proposal describes the mass spectrometry requirements of the University of Texas Health Science Center at San Antonio which cannot be met by instrumentation either at the Health Science Center or in the San Antonio area. The limitations of the current facility include: no means for direct introdution of an HPLC eluate into the mass spectrometer; an upper mass limit of 1000 amu, when many investigators need measurements up to 3000 amu; no techniques available for ionization of thermally-labile, non-volatile substances; inflexibility for modification to meet future requirements. Among the features of the requested Finnigan MAT212, automated by an INCOS 2200 system, are the following: direct HPLC interface; upper mass limit of 3600 mau; Fast Atom Bombardment (FAB) source for ionization of thermally-labile, non-volatile compounds; capability for in-field modification to accept additional options, such as measurment of negative ion mass spectra. The Mass Spectrometry Laboratory at the Health Science Center currently provides support for many projects funded by NIH. The continued success of these projects is dependent on expanding the mass spectrometry facility to accommodate the increasing complexity of the biomedical research being carried on at this institution.